Grinding machines



Feb. 11, 1969 H. A. DROITCOUR 3,426,433

GRINDI'NG MACHINES Filed-March 31. 1965 V Sheet INVENTOR.

HOWARD A. DROITCOUR BY 1969 H. A. DROITCQUR I 3,426,433

GRINDING MACHINES riled March 31. 1965 Sheet 2 of 35 F l G. 4 1 I ./4/

ma Z57 HOWARD" A. DROITCOUR BY Feb. 11, 1969 DRQITCOUR 3,426,483

GRINDING MACHINES Filed latch 31, 1965 Sheet 3 0f 5 I N VE N'TOR. A HOWARD A. DROITCOUR ATTORNEYS Feb. 11 1969 14,5, DRQITCQUR 3,426,483

GRINDING MACHINES Fi led March 31. 1965 INVENTOR. HOWARD DROITCOUR Sheet INVENTOR. HOWARD A; DROITCOUR fidww figfififs H. A. DROITCOUR GRINDING MACHINES Feb. 11, 1969 Filed March 51, 1965 United States Patent 3,426,483 GRINDING MACHINES Howard A. Droitcour, 374 Meshanticut Valley Parkway, Cranston, RI. 02910 Filed Mar. 31, 1965, Ser. No. 444,165 U.S. Cl. 51-165 Int. Cl. B241: 49/00, 51/00 21 Claims ABSTRACT OF THE DISCLOSURE This invention relates to both internal and external grinding machines.

A major object of the invention is to grind flexible work pieces to very fine tolerances of truth and size quickly and efliciently.

Another object is to grind work pieces, whose geometry requires flexible grinding spindles, to close tolerances of size and truth quickly and efiiciently.

To achieve these objects the out-of-truth or out-of-size of the work is measured at various positions and then this information is used to cause greater grinding forces at the positions needing more stock removal. In one method, the grinding force is planned to cause removal of stock in porpoition to the amount of stock needing to be removed. With such an arrangement, positions needing no stock removal receive no grinding pressure, and each position needing stock removal receives a grinding force in proportion to the amount of stock needing to be removed. Since only the positions needing grinding are ground, truth is quickly established. In another method pressure may be applied and then released as on-off rather than a proportional method.

With reference to the drawings:

FIG. 1 is a diagrammatic view illustrating certain outof-round grinding;

FIG. 2 is a side elevation of a grinding machine for external grinding diagrammatically showing the elements of this invention;

FIG. 3 is a plan view of the machine of FIG. 2;

FIG. 4 is a plan diagrammatic view of a machine modified for internal grinding and partly in section;

FIG. 5 is a sectional view on line 55 of FIG. 4;

FIGS. 6, 7 and 8 are diagrammatic views showing the mounting of the grinding wheel such as used in internal grinding;

FIG. 9 is a plan view partly in section diagrammatically showing a modification for grinding long holes;

FIG. 10 is a sectional view of :a work piece of a particular shape to which this invention may be applied;

FIG. 11 is a section on line 11--11 of FIG. 10; and

FIG. 12 is a plan view partly in section diagrammatically showing a modification for applying positive on and olf pressure.

When a conventional grinder is grinding a work piece that is flexible in varying amounts in different directions, the resulting surface being ground will not be truly round because the amount of deflection due to grinding pressure will vary with the siffness as the direction of the force moves around the surface being ground. The resulting out-of-round for such a shaft, as for example a crank shaft, might be somewhat like that illustrated in FIG. 1.

3,426,483 Patented Feb. 11, 1969 Here the work piece 1 is being ground by the grinding wheel 2 at position 3. The force of the grinding bends the shaft an amount 4 in this position 3.. However when positron 5 is being ground, the same force will cause a larger bend in the shaft, such as the amount 6, because the shaft is more flexible in this direction. The present invention eliminates this variation by the use of an apparatus illustrated in FIG. 2 and FIG. 3.

In FIGS. 2 and 3 a workpiece 7 is mounted between centers 8 and 9 as in a conventional grinding machine. The centers are supported on a table 10 that is movable with respect to base 11 along the center axis of the work as indicated by arrows 12. A grinding wheel 13 is carried on a table 14 that can be adjusted to and from the axis of the work as shown by arrows 15 with respect to base 11 by some means as at 16. The grinding wheel is supported by bearings in lever 17 which is connected to table 14 thru reeds 18 and 19 and the wheel is driven by a belt from motor 13. The lever 17 is also connected to table 14 by spring 20. A transducer 21 that is rigidly supported by table 14, acts to raise the end 17' of lever 17 proportionally as the electrical current supplied through wires 22 increases such as by a solenoid and electric magnet. As the transducer raises the lever 17, the grinding wheel moves into the work piece, pivoting about the reeds 18 and 19 to press the grinding wheel with more force into the work piece. This arrangement allows for movements of the wheel 13 to and from the work piece controlled by an electrical current supplied to the transducer 21.

The surface being ground is measured for size and truth by a gage 23 that has a feeder 24 to contact the work. This gage is set so that it will indicate the amount of stock left on the workpiece over the finish size or over any intermediate size chosen to approach the finish size. The record of this oversize is recorded on a magnetic tape that is fastened to the surface of the cylinder 24.1, that is geared by gears 25, 25, 25 to the work piece through the driving head. This magnetic tape record is taken for each position around the surface and recorded on the tape by transducer 26. It can be recorded continuously while the grinding is going on, if the pickup feeler is located in a position approximately from the grinding contact where the deflection of the shaft from the grinding pressure'has a minimal effect on the size measurement. An alternate way is to record the amount of oversize on the magnetic tape when no grinding is being done.

The record of oversize thus made is now used by being picked up from the tape by transducer 27, amplified in amplifier 28, and introduced into transducer 21 in the correct timing so that while a particular position is being ground, the transducer is receiving the signal from-the tape that was recorded for that position. The arrangement is zeroed-in so that when the final size is reached, no grinding pressure will be applied.

The record on the tape may be visualized by thinking of this record as a tone of varying volume. When the feeler is at the zero oversize position (that is, at the finish size) the volume would be minimal. As the feeler is lifted to record a small amount of oversize, the volume of the tone would increase. As the feeler is: lifted to record the maximum oversize, the loudest tone would be recorded on the tape. Later, this recorded tone is picked up by transducer 27, amplified by amplifier 28, and used to produce in transducer 21 a force proportional to the volume of the recorded tone. In this way, the force of the grinding wheel on the work is maintained proportional to the oversize at the position being ground. With this method, the correct size is reached quickly while maintaining a true surface at the time the finish size is reached.

Grinding internal holes to close tolerances is difiicult whenever the geometry of the work piece requires grinding-wheel spindles that are flexible. If a form is being ground, the angle of the Wheel face resulting from the deflection of the spindle due to grinding pressure is often large enough to be a factor in maintaining tolerances.

FIGURES 4 and 5 show the invention as applied to an internal grinder. The work head 30 rotates about an axis 31 and carries a work piece 32 shown in section in FIG. 4. The grinding wheel 33 is carried on a spindle 34 which is supported by bearings in housing 35. Housing 35 is connected to table 36 by means of reeds 37 and 38. The table 36 can be moved in ways 36 to position the grinding wheel along the axis of the work piece and also along ways 36 into the work piece to accomplish the grinding. A gage 39 has a feeler 40 so arranged that it can contact the work piece on the surface being ground. The gage is set to record the amount of stock needing to be removed to reach the finish size or to reach any selected size approaching the finish size. This undersize is recorded on a magnetic tape geared to the motion of the work piece, much as was described earlier for the external grinder, by gage 39, magnetic tape in cylinder 24 driven by gears 25 and 25 and 25, so that a record of the undersize will be obtainable for each position along the surface of the work piece as it is rotated through one turn. Later, this record is picked up from the tape by transducer 26 and amplified at 28 so that it can operate transducer 41. The pick-up is so timed that while a par ticular position is being ground, the transducer is receiving the signal from the tape that was recorded for that position.

When the transducer is receiving a signal of zero-underside from the tape, the grinding wheels cutting surface is to be adjusted to the finishing position by moving the table 36. The pressure of the grinding wheel against the work piece would the zero if there were no undersize at this point. If there were some undersize at a given position, the grinding wheel would be forced back the amount of the undersize, bending the grinding spindle and causing a grinding pressure that this bend produces. When the grinding spindle is comparatively flexible, a small amount of undersize produces very small grinding pressures. However, when a small amount of undersize is recorded on the tape, it can be amplified and supplied to the transducer 41 to force the wheel into the work, producing a bend in the arbor many times that produced by the undersize alone. This enables more rapid reduction of stock needing to be removed and therefore establishes truth and size to given tolerances more quickly.

The purpose of the reeds 37 and 38 is to establish a pivot point 42 about which the housing 35 will pivot when acted up by transducer 41. This point 42 is selected to minimize any change in angle between the face of the grinding wheel and the face of the work piece, that may occur when transducer 41 bends the spindle 34 to produce a greater grinding force. The action is illustrated in FIG- URES 6, 7 and 8. FIGURE 6 shows a grinding spindle 50 holding a grinding wheel 51 at a time when it is held by housing 52 so that it is just touching the work piece 53 but has no grinding pressure. FIGURE 7 shows the same elements at a time when there is a grinding pressure caused by the moving of the spindle bearing housing 52 a distance 54 to a new position 55 of the axis that is parallel to the former position 56 shown in FIGURE 6. The spindle 50 bends an amount 54 and in so doing forms an angle 57 between the face of the work piece 53 and the face of the grinding wheel 51. This change of face angle has many disadvantages so the use of a motion to increase pressure without changing this angle is shown in FIGURE 8. Here a pivot point 58 of the housing 52 is selected approximately one-third the length of the flexible spindle from its base. As the housing 52 is pivoted through angle 59 to increase the pressure on the work it bends the arbor an amount 60. The angle 61 formed by the face of the wheel 51 to the axis 62 will be very nearly equal to the angle 59. If they are equal, the angle 63 between the faces of 51 and 53 would be zero. By adjusting the pivotal position 58 along the axis, a point can be found where the change of angle 63 is negligible for the particular conditions encountered. The machine is set by the operator so that the finish size will be achieved when the angle 59 is zero and there is no grinding pressure. Then any needed grinding pressure is added by pivoting around point 58. This adds grinding pressure without changing the angle 63. The compensated grinding machine will use large-r grinding forces than an uncompensated grinder especially during the finishing of close tolerance holes. At such time the maintenance of consistent face angles over a large range of grinding pressure is particularly important. Therefore the use of a method that adds pressure while maintaining consistent positions is especially useful.

In FIGURE 9 the work piece 70 is held in a spindle 71 that rotates with respect to base 72 about an axis 73. A grinding wheel 74 is held on a spindle 75 which is supported by bearings in housing 76. This housing is supported by reeds 78 and 79 so that it will pivot about point 77. Reeds 78 and 79 are fastened to table 80 which is movable in ways 80 in base 72 so that the grinding wheel can be positioned along the axis of the work piece 70 and also ways 80" for movement perpendicular to the axis to engage the work piece. The housing is also restrained in its motion about point 77 by a spring 87 that connects the housing 76 to the table 80. A transducer 81 is arranged to measure any motion between the housing 76 and the table 80. The signal from the transducer 81 is amplified electrically in amplifier 88 and recorded by transducer 89 on a magnetic tape that is located on the surface of the cylinder 86. Transducer 89 is moved axially of the work by table 80 so that a record of each axial position may be recorded. The cylinder 86 is driven by gears 83 and 84 so that there is an exact and repeatable relationship between the work piece and the magnetic tape on the surface of cylinder 86. The grinding wheel 74 is fed through the work piece 70 axially by means that can be accurately repeated, as for example a screw 82 driven by gears 83 and 84 and engaged by the half-nut 85 that can be engaged and disengaged from screw 82.

The operation of recording the undersize of the hole in work piece 70 is done as follows. Table 80 is adjusted so that the grinding wheel is in a position to finish the hole to a given size if there were no deflections in the machine. Then a recording pass is begun in which the grinding wheel 74 is fed axially through the work piece 70. The grinding wheel now acts as a feeler of a gage that measures the undersize of the work piece for each rotational and axial position of the surface being ground. The amount of stock needing to be removed forces the grinding wheel 74 back the amount of the undersize in that position. This causes a motion of the housing 76 which is picked up by transducer 81, amplified in amplifier 88 and recorded on the magnetic tape by transducer 89. Thus, as the recording pass is made, the amount of stock needing to be removed is recorded for each position of the grinding wheel 74 as it passes through the work piece 70.

Later, on a work pass of the grinding wheel 74 through the work piece, this record of the needed stock removal is picked up by transducer 89, amplified by amplifier 88 and sent to transducer 90 to place a force on housing 76 in the direction to force the grinding wheel 74 harder into the work piece 70. The force of the transducer 90 acting on the housing 76 is arranged to be substantially proportional to the amount of stock needing to be removed. When the forces are proportional to the stock needing to be removed, the force will be zero when no stock has to be removed. This is important because once the finish size is reached, no more stock will be removed.

After the hole is ground with one or more work passes,

the record on the tape is erased and a new record of stock to be removed is recorded during a new recording pass. This record is used for additional grinding and so on.

The use of the grinding wheel 74 as the feeler and the spindle 75 and housing 76 as part of a gage with transducer 81 has certain advantages. However, any method of gaging the stock needing to be removed in various positions could be used to record this information on a magnetic tape. Later during the grinding operation it could be timed in to arrange for greater grinding pressures in positions needing more stock removal.

These same thoughts could be applied to surface grinding of flat pieces that were flexible in varying amounts in different positions. They might also be used in contour grinding where the set-up required flexible components as grinding wheel spindle or supports.

Another object of the invention is to produce a contoured surface that varies slightly from a true cylinder.

It is often necessary to machine a hole that is contoured to a desired shape slightly varying from a true cylinder. Such a hole is shown in FIGURE 10, where the diameter varies at various positions 91, 92 along the axis of the piece. It may also be necessary to vary the radius at positions around the circumference as shown at 93, 94 in FIGURE 11. There is often a desirable shape that includes a combination of both shapes in FIGURES and 11.

These shapes are machined by use of a machine as shown in FIGURE 9. The hole is first ground cylindrically to such a size that it just finishes the contour shape at positions of the smallest radius. A tape is prepared that will add pressure in the position needing stock removal to complete the contoured shape desired. This is done by moving the tape to the proper position and recording a magnetic signal by hand that is required for that position. On more complicated requirements a cam held in the Work spindle can be prepared so that it actuates the feeler on the gage used to record on the magnetic tape. Since the force of grinding is instantaneously controlled for any grinding position, any contoured shape within the capacity of the machine may be produced.

Another method of using a magnetic tape to control the pressure of the grinding wheel against the work piece is shown diagrammatically in FIGURE 12. FIGURE 12 shows the elements of a machine similar to that shown in FIGURE 9. The control in FIGURE 12 uses an onoff method of adding pressure rather than a proportional method described for FIGURE 9. In FIGURE 12 a work piece 101 revolving about an axis 102, is being ground by a wheel 103 which is held by a spindle 104.

The spindle 104 is held in bearings 105 in housing 106. Housing 106 is made to pivot about point 107 by its supporting reeds 108. Reeds 108 are carried on table 115 which is movable on ways to carry the grinding wheel through the work and to and from the work to accomplish the grinding. A transducer 109 is arranged electrically so that when the on signal is received from the tape, it forces the housing 106 against the stop 110 which is carried on table 115, so that the grinding wheel 103 presses harder into the work piece 101. This stop may be adjusted to a position where the grinding wheel will remove a given amount of stock during one work pass, as for example .0001 inch. The amount of bend in the spindle to produce .0001 inch stock removal would ordinarily be many times the stock removed, as for example .002 inch or twenty times the stock removal of .0001 inch. With a machine so set the grinding is accomplished as follows. The machine is set tomake a recording pass with table 115 adjusted so the grinding wheel 103 just touches the work piece. Whenever the work piece presses against the wheel more than .0001 inch, the electrical apparatus makes an on record on the magnetic tape. Whenever the work piece is pressing against the grinding wheel less than .0001 inch, the electrical apparatus is set to record an off indication on the tape. A complete recording pass is made that indicates the on and off positions throughout the work piece. Then a work pass is begun. The electrical apparatus is arranged to energize the transducer 109 when the on signal is indicated. When transducer 109 is energized it moves the housing 106 against the stop 110, thus producing a grinding force that will remove about .0001 inch from the work piece at this position. This constant force is continued as long as the signal from the tape is indicating on." When the tape signals off the transducer 109 is de-energized and allows spring 111 to return the housing 106 to the limiting stop 112. When the housing 106 is against stop 112, the grinding wheel is in the neutral or beginning position where no grinding force is added by the electrical mechanism. When the housing 106 is in this neutral position against stop 112, the machine is set so that there will be no grinding pressure at those positions where the indication is off.

After this work pass is completed, a recording pass is performed without changing the set of the machine for hole size. If there are any positions that still need .0001 inch stock removal to achieve this size, they will be recorded as on positions. Then a second work pass is run. The position needing grinding will be reduced by being ground with a force produced when the housing is against stop 110. Successive recording and work passes may be continued until all points needing grinding to achieve that size to which the machine is set have been ground. The machine is then advanced to grind a slightly larger hole in the work piece and the process repeated until the new size has been ground. By repeating this process the hole can be ground to a desired size, and each position being ground will be within .0001 of its proper size.

If a closer or finer limit is desired, the stop 110 can be adjusted closer to housing 106 so that the grinding pressure added by transducer 109 when the tape signal is on," is suflicient only to remove a smaller amount of stock from the work piece, as, for example, .00001 inch. With this new setting a similar process of recording and work passes is continued until the hole is within .00001 inch tolerance of size. This can be changed to accomplish any given tolerance required for the work within the capability of the machine.

Both the on-off and the proportional methods of using the invention have advantages and disadvantages, the choice of method being determined by the type of work expected to be handled by the grinding machine.

I claim:

1. In a grinding machine, a grinding wheel, supporting parts for the grinding wheel and a work piece, means to apply working pressure between the work piece and the grinding wheel during a cycle of operation resulting in a relative bending of the supporting parts therefor, means to measure and make a record of the thickness at selected positions along a surface to he ground of stock to be removed from the Work piece in order to achieve a desired shape, and means to pass the grinding wheel in a path over the surface to be ground in a selected repeatable pattern and to vary the working pressure along the path in accordance with said record to compensate for said bending.

2. In a grinding machine as in claim 1 wherein the record is on a magnetic tape.

3. In a grinding machine as in claim 1 wherein the grinding wheel is mounted on a spindle in a bearing housing and there is provided means for increasing pressure of the grinding wheel on the work piece by pivoting the grinding wheel spindle bearing housing about a point where the change in angle of the housing substantially equals the angular deflection of the grinding wheel spindle Where the grinding wheel contacts the work piece.

4. In a grinding machine as in claim 1 wherein the grinding wheel is mounted on a spindle in a bearing housing and there is provided means for adding pressure of the grinding wheel on the work piece using a pivoted grinding wheel spindle bearing housing to neutralize any change of attitude of the grinding Wheel to the work piece caused by the bending of the grinding wheel spindle.

5. In a grinding machine as in claim 1 wherein the grinding wheel is mounted on a spindle in a bearing housing and there is provided means to compensate for any angular deflection of the grinding wheel spindle due to grinding pressure arranged to hold constant the angle between the contact of the grinding wheel and the work piece by pivoting the grinding wheel spindle bearing housing.

6. In a grinding machine as in claim 1 wherein there is provided a magnetic tape and a transducer and means connecting each individual position of the grinding wheel along a pattern being ground with a corresponding individual position of the transducer along the magnetic tape.

7. In a grinding machine as in claim 1 wherein said means to measure and make a record uses the grinding wheel as the feeler to contact the work piece.

8. In a grinding machine as in claim 1 wherein the means to measure and make a record includes a magnetic tape to record the radial amount of stock to be removed from a substantially cylindrical surface being ground in order to finish a work piece to a desired shape as the radial amount of stock needing to be removed varies along the path selected for the grinding wheel to pass when grinding the work piece.

9. In a grinding machine for a work piece from which a varying amount of stock is to be removed to achieve a desired shape, a grinding wheel to remove stock from the work piece when forced against the work piece, means for supporting the grinding wheel and the work piece, means comprising a gage for making a record of the varying amount of stock to be removed from difierent areas of the work piece, and means responsive to the record to vary and control the force of the grinding wheel against the Work piece.

10. In a grinding machine as in claim 9 wherein the gage has a feeler engaging the work piece.

11. In a grinding machine as in claim 9 wherein the grinding wheel operates the gage for the record.

12. In a grinding machine as in claim 9 including means for amplifying the pressure between the wheel and work piece.

13. A grinding machine as in claim 9, wherein the means responsive to the record includes means for the application of selected increments of grinding pressure.

14. A machine as in claim 9 wherein the means for supporting the grinding wheel includes a spindle that flexes and a pivot means for said spindle so that an angular change about the pivot means causes a change in grinding pressure.

15. A grinding machine as in claim 14 wherein the pivot means causes pivoting about a point along the axis of the grinding wheel spindle where the change in angle used to alter the grinding pressure substantially equals the angular deflection of the spindle where the grinding wheel contacts the work piece.

16. A grinding machine as in claim 14 wherein the pivot point of the pivot means is located at a point selected to minimize the change in angle between the grinding wheel and the work piece as the. grinding pressure is changed by pivoting of the spindle.

17. In a grinding machine for removing stock from a work piece, means for mounting a work piece, a rotating grinding wheel, means to move the work piece relative to the grinding Wheel to engage and apply varying pressures between the grinding wheel and work piece, means to make a recording of the amount of stock to be removed, and means to vary the pressure of the grinding wheel against the work piece in accordance with said recording.

18. In a grinding machine, a grinding wheel, means for supporting the same, means for supporting a work piece, means to apply working pressure between the work piece and the grinding wheel during a cycle of grinding operation resulting in a relative bending of the supporting means, means to measure and make a record of the thickness at selected positions along a surface to be ground of stock to be removed from a work piece while under said working pressure in order to achieve a desired shape where relative bending due to pressure of grinding occurs and means to vary and control the force of the grinding wheel against the work piece at different positions responsive to the record of the stock to be removed for said different positions to compensate for said bending.

19. In a grinding machine as in claim 18 wherein said means to measure and make a record is located in a position to contact the work piece where distortion of the work piece due to grinding pressure while the work piece is being ground least alfects the means to measure.

20. In a grinding machine as in claim 18 wherein said means to measure and make a record is located in a position to contact the work piece at substantially right angles to the application of pressure between the work piece and grinding wheel.

21. In a grinding machine for a work piece from which stock is to be removed to achieve a desired shape, a grinding wheel to remove stock from the work piece when forced against the work piece, means for supporting the grinding wheel and work piece, means to pass the grinding wheel over the work piece, means comprising a gage for making a record on a recording pass of a force due to the bending that occurs when the grinding wheel is set in a position to achieve the desired shape if no bending occurs and means to amplify the varying pressure of the grinding wheel against the work piece in proportion to the varying bending forces recorded during a grinding pass of the grinding wheel along the Work piece.

References Cited UNITED STATES PATENTS 2,861,399 11/1958 Lundius 51-165 X 3,197,921 8/1965 Hohler et al. 51165 X 3,269,064 8/1966 Lockwood 51-48 3,274,738 9/1966 Kuniholm 51-165 FOREIGN PATENTS 802,206 10/1958 Great Britain.

LESTER M. SWINGLE, Primary Examiner. 

